Listening devices are sneakier than cameras: they have no lens, reflect no light, and can sit inside an outlet, a car or a meeting table for years unnoticed. Still, they cannot escape physics — they draw power, leave electromagnetic traces and usually transmit data. This guide shows how to sweep your space along those traces.
Know the types of bugs
GSM bugs carry a SIM card and stream room audio live over the cellular network; they usually hide in outlets, extension cords or car electronics for constant power. WiFi/Bluetooth transmitters send audio over the local network. Pure recorders save to memory without emitting any signal — the hardest type to detect, requiring a physical search.
When to get suspicious
- Someone knows the content of a private conversation they shouldn't.
- Objects that newly appeared or moved: outlets, adapters, pens, smoke detectors.
- Cables or taped-on boxes in your car or office that aren't yours.
- Rhythmic interference from speakers during phone calls (a possible sign of a nearby GSM transmitter).
Hear active devices with ultrasonic analysis
Many active recording and transmitting devices produce a faint but characteristic noise in the 18-22 kHz band, beyond human hearing. A live spectrum analysis through your phone's microphone makes that signature visible.
For accurate results: stand still, close windows and doors, and repeat the scan at different spots in the room. A persistent narrow-band peak means you should search for its physical source.
Find hidden electronics with EMF measurement
Every powered circuit distorts the magnetic field around it. Take a baseline with your phone's magnetometer, then slowly sweep suspicious walls, frames, outlets and objects from 5-10 cm away. A sudden delta spike away from known appliances (TV, microwave, fridge) points to embedded active hardware.
This also works against pure recorders that emit no signal — a battery and circuit cannot hide their magnetic footprint.
Don't skip the network and Bluetooth layers
Devices streaming audio over WiFi show camera-like signatures in a network scan; Bluetooth recorders appear as anonymous devices in a BLE scan. Investigate the vendor and open ports of every unfamiliar device on your home or office network.
SenseRadar combines all of these layers — ultrasonic, EMF, WiFi, BLE — in a single sweep, with every analysis staying on your device. If the stakes are high (e.g. corporate espionage), have your findings verified by a professional TSCM team.